Exploring the Potential of Flavobacterium covae Catalase and DNA Starvation/Stationary Phase Protein as Recombinant Protein Vaccines Against Columnaris Disease in Channel Catfish

Authors: CHURCHMAN, EMILY - Auburn University; Lange, Miles; SANKAPPA, NITHIN - Orise Fellow; QUIROZ, VICTORIA - Auburn University; DESILVA, ASHLEY - Auburn University; Justice, Megan; Abernathy, Jason; LILES, MARK - Auburn University

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2025
Publication Date: 7/31/2025
Citation: Churchman, E., Lange, M.D., Sankappa, N.M., Quiroz, V., Desilva, A., Justice, M.E., Abernathy, J.W., Liles, M.R. 2025. Exploring the Potential of Flavobacterium covae Catalase and DNA Starvation/Stationary Phase Protein as Recombinant Protein Vaccines Against Columnaris Disease in Channel Catfish. Fish and Shellfish Immunology. 166: Article 110600. https://doi.org/10.1016/j.fsi.2025.110600.
DOI: https://doi.org/10.1016/j.fsi.2025.110600

Interpretive Summary: Columnaris disease, caused by Flavobacterium covae, is a principal cause of mortality in channel catfish that can lead to several million dollars in annual production losses. This Gram-negative bacterium is an opportunistic pathogen that manifests as a biofilm on the host's mucosal surfaces as the disease progresses. We have previously demonstrated the effectiveness of using recombinant protein technology to develop a bath immersion vaccine against columnaris disease. The current work has sought to evaluate additional F. covae recombinant protein vaccine formulations through bath immersion delivery. The catalase and DNA starvation/stationary phase proteins were cloned and expressed in E. coli and purified under native conditions. Different groups of fish were vaccinated with the recombinant protein(s) mixed with an immersion adjuvant or sham immunized with adjuvant alone. Nine weeks post-immunization, all groups were challenged with F. covae and the vaccinated groups showed significant increases in survival (13-45%) when compared to the adjuvant only control group. Additional delivery strategies to enhance the catfish immune response to F. covae recombinant protein vaccines is underway to optimize their use in the production environment.

Technical Abstract: Columnaris disease, caused by Flavobacterium covae, is a principal cause of mortality in the channel catfish industry that can lead to several million dollars in annual production losses. This Gram-negative bacterium is an opportunistic pathogen that manifests as a biofilm on the host's mucosal surfaces as the disease progresses. Recent work in our lab identified the upregulation of specific F. covae biofilm genes after stimulation with channel catfish mucus. We have previously demonstrated the effectiveness of using recombinant protein technology to develop a bath immersion vaccine against columnaris disease. The current work sought to evaluate additional F. covae recombinant protein vaccine formulations through bath immersion delivery. Catalase and DNA starvation/stationary phase proteins were cloned and expressed in E. coli and purified under native conditions. Different groups of fish were immunized with the recombinant protein(s) mixed with an immersion adjuvant or sham immunized with adjuvant alone. Nine weeks post-immunization, all groups were challenged with F. covae and the vaccinated groups showed significant increases in survival (13-45%) when compared to the adjuvant only control group. No antigen specific skin mucosal IgM antibodies were detected via ELISA; however, RT-qPCR analyses of innate and adaptive immune genes indicated the priming of an adaptive immune response likely occurred among the vaccinated groups. Additional delivery strategies to enhance the catfish immune response to F. covae recombinant protein vaccines is underway to optimize their use in the production environment.